It is well known that precision manufacturing processes, such as precision metal working, require that the tools used be made of hard, tough material which will maintain sharp, accurate cutting edges for as long as possible for economic reasons. It is also well known that grinding is the most effective means for shaping and sharpening the cutting edges of these hard, tough tools. The advent of computer control of machines has greatly enhanced the benefits of more precise tooling and longer lasting tooling.
Certain types of rotating cutting tools have a mounting shank at one end only and, therefore, can be supported at one end only, during manufacture, during subsequent maintenance, and during use. This is because the unsupported ends of these tools, as well as the sides, include cutting edges and therefore must be accessible. The primary object of the present invention is to provide an improved method and apparatus for the manufacture and maintenance of such end mounted precision rotary cutting tools.
In conventional tool grinding apparatus for end mounted rotary cutting tools, the tool is mounted horizontally with the cutting end essentially unsupported. Thus, the tool's weight creates a continuously changing overhanging moment reacting against the bearings as the tool is moved horizontally past the grinding wheel. The tool grinding apparatus disclosed in Homberg's U.S. Pat. No. 2,035,163 exemplifies well known prior art in this field. Increasing demands for tool grinding accuracy led to improvements in tool grinding apparatus by applying pressurized fluid film bearings, such as those shown in U.S. Pat. No. 3,112,140, issued to C. R. Adams. Air is used as the bearing fluid in most tool grinding apparatus; however, other gases and liquids (such as water or oil) can be used. Increases in the size and/or length of end mounted cutting tools necessitated further improvements to alleviate the effect of the greater overhanging moments encountered with the horizontally positioned, long and/or heavy tools. The invention of U.S. Pat. No. 3,432,213, "Self-Leveling Air Bearing Fixture", issued to C. R. Adams, is an example of such further improvements and was made in response to the need to reduce the effects of the overhanging loads. However, the continued requirement for improvements in manufacturing technology based on the economic benefits obtainable using computer techniques and, in some cases, larger tools has again created a need for greater accuracy in the shaping and sharpening of larger, longer end mounted tools. Known tool grinding apparatus does not meet this need, largely because of the inaccuracies resulting from the greater overhanging moments produced by the horizontally mounted longer, heavier tools. A tilt as small as 0.0002 inch can create unacceptable inaccuracies in the grinding of long, large tools.